This invention relates to the art of staple pullers, and particularly to the art of hand-held staple pullers of the type having coacting cam surfaces that engage and remove a staple.
A well-known staple remover comprises two pivotally attached parts that have cam surfaces at their respective ends. The device is held in the hand of a user, and the two parts are squeezed together by the user after the tips of the cams have been engaged with the staple. The bight of the staple is moved along the cam surfaces as the parts move toward each other to lift the staple and remove it from an object.
A common problem with this type of staple remover is that the staple is sometimes pulled from the object in an uneven manner (FIG. 6), which typically results in one leg remaining lodged in the object while the other leg is free. Another similar problem is that the staple is often broken by the action of the puller, leaving the part remaining in the object separate from the remainder of the staple. The flat parts of the known staple remover adjacent the cam surface do not permit secure gripping of the staple as this would interfere with the removal of subsequent staples.
Various arrangements have been proposed to allow the part of the staple that remains in the object to be grasped by the staple puller in a manner that does not rely on the action of the cam surfaces. One such arrangement is shown in U.S. Pat. No. 3,311,346 (Almond, Jr.). The staple remover according to this patent includes a block mounted in each of the channel-like parts of the staple remover such that the staple can be grasped between the blocks and pulled out. U.S. Pat. No. 4,921,216 (Krulich) shows a staple remover of the same general type wherein one of the cam surfaces has a notch for receiving the staple and for holding the staple securely by a force applied by the cam surface of the other part.
Arrangements similar to that of Krulich are shown by U.S. Pat. Nos. 858,257 (Breiding), 2,431,922 (Curtiss), and 4,869,464 (Davidson).
U.S. Pat. No. 4,944,491 (Kirk) teaches a staple puller wherein the cam surfaces are flanked by protrusions that expand the legs of the staple. U.S. Pat. No. 499,637 (Knight) shows yet another type of staple extractor.
U.S. Pat. No. 5,513,833 issued to Kirk discloses a rigid tongue member affixed to the base and between the sides of the lower jaw. The staple remover also includes a resilient member between the opposite jaws. The resilient member is designed to guide the staple so that it does not move up and over the opposite tongue-shaped piece. The problems with the design include the fact that the rigid member is not designed to trap the staple but is designed so as to tend to make the staple move up and over it against the resilient member. Also, it consists of two additions to the standard staple remover which adds to the complexity of manufacture. Another drawback to this arrangement is that the angled top section 76 appears to extend below the point of the jaw such that when one end of the staple exits the paper and the other end is caught, the free end would be capable of sliding over the angled section.
U.S. Pat. No. 4,903,945 issued to Wang discloses a centrally located engaging member that is located between the sides of one of the jaws and forms a slot with the sides of the jaws. The engaging member engages with the upper surface of the staple to thereby anchor the staple at a middle portion thereof for withdrawal of the staple ends from the paper. Wang does not disclose a flat surface forming a notch along the cam surface and providing a back-up method of gripping and removing an end of a staple if all else fails. Also, the central engaging member is disposed substantially parallel to the paper which in effect holds the center of the staple down against the paper when the curved jaws are encountering the greatest resistance trying to bend the legs of the staple to lift the staple away from the paper.
What is needed is an improved staple remover capable of removing staples such that both ends of the staple are removed and that has a gripping surface for removing staples that break or otherwise need to be pulled.
The present invention meets the above described need by providing a staple puller, of the type having two pivotally mounted parts and cam surfaces at the ends of each of the parts, with a bridge member connected to one of the narrower jaws of the device and extending across the opening between the jaws to form a stop and a pressure point for pulling staples.
In the preferred embodiment, the staple puller of the invention has a pair of spring-biased jaws with opposing cam surfaces. One set of jaws is spaced farther apart than the other pair such that the narrower jaws slide into the opening between the wider jaws. The sides of the narrower jaw are provided with a bridge member disposed thereon. The bridge member has a thickness approximately equal to the thickness of the jaw. The bridge member extends across the gap between the pair of jaw members of the narrower jaw such that it extends all the way across the opening and rises above the cam surface. The bridge member extends beyond the sides of the lower jaws such that it engages with the upper jaws. The bridge member forms a stop on the cam surface and provides a gripping surface formed between the top surface of the wider jaws and the top of the bridge member.
An engaging member is disposed between the sides of the jaws and is preferably supported from the bridge member. The engaging member extends between the sides of the narrower jaw and is preferably disposed at an angle proximate to the curved jaws such that a space is formed between the jaws and the underside of the engaging member. The space is provided to capture the staples at the beginning of the removal process.